O₂ Extraction During Exercise Determines Training Effect After Cardiac Rehabilitation in Myocardial Infarction

Abstract

Correlations between baseline hemodynamic and oximetric variables during an invasive exercise test and an improvement in peak oxygen uptake (peak Vo₂) after exercise training (ET) were examined in 20 patients who participated in a cardiac rehabilitation program after acute myocardial infarction (AMI). Peak Vo₂ significantly increased by 23±21% (p<0.01) after ET and the improvement best correlated with the change in O₂ extraction fraction ([arterial O₂ content - venous O₂ content] / arterial O₂ content) during an exercise test before ET (r=-0.61, p<0.01). Exercise capacity was improved to a greater extent by ET in patients with a smaller increase in O₂ extraction fraction during an exercise test before ET. Thus, O₂ extraction fraction during an exercise test before ET may be a useful predictor of the improvement in exercise capacity after ET in post-AMI patients. (Circ J 2002; 66: 891 - 896)